An oxidation reaction is one of the most basic reactions in the field of organic chemical industry, and various oxidation processes have been developed. From the viewpoints of resources and environmental issues, a catalytic oxidation process, in which molecular oxygen or air is directly used as an oxidizing agent, is preferred. However, the catalytic oxidation process generally requires high temperatures and/or high pressures for activation of oxygen or, alternatively, must be performed in the co-existence of a reducing agent such as an aldehyde to proceed the reaction under mild conditions. Accordingly, such a conventional catalytic oxidation process cannot easily and efficiently produce an alcohol or a carboxylic acid under mild conditions.
Lower hydrocarbons such as methane and ethane are nitrated using nitric acid or nitrogen dioxide at high temperatures of from 250° C. to 300° C. However, when a hydrocarbon having a large number of carbon atoms is nitrated under the above condition, the substrate is decomposed, and a target nitro compound cannot be obtained in a high yield. To nitrate hydrocarbons, a method using mixed acid (a mixture of nitric acid and sulfuric acid) is widely employed. However, this method requires large amounts of a strong acid in a high concentration.
Additionally, few processes are known for efficiently and directly introducing carboxyl groups into hydrocarbons under mild conditions.
A variety of processes are known for producing organic sulfur acids or salts thereof. For example, processes for producing a sulfonic acid include a process of oxidizing a thiol or disulfide with an oxidizing agent, a process of allowing an aromatic hydrocarbon to react with anhydrous SO3-pyridine or chlorosulfuric acid by using a Friedel-Crafts reaction, and a process of synthetically obtaining a sulfonic acid by subjecting an unsaturated compound to free-radical addition. These processes, however, require extreme reaction conditions or inevitably produce large amounts of by-products. Additionally, no processes for directly and efficiently sulfonating non-aromatic hydrocarbons have been known.
Processes are known in which a variety of compounds are added to unsaturated compounds each having a carbon-carbon double bond or heteroatom-containing compounds and thereby yield useful organic compounds. For example, when an active methylene compound such as a malonic diester is allowed to react with an olefin having an electron attractive group, such as acrylonitrile, in the presence of a base, a carbon-carbon bond is formed as a result of a nucleophilic addition reaction and thereby yields an addition product (Michael addition reaction). When two types of carbonyl compounds are treated in the presence of an acid or a base, one carbonyl compound is nucleophilically added to the other to form a carbon-carbon bond and thereby yields an aldol condensate.
These processes, however, are generally performed in the presence of an acid or base and cannot be applied to compounds each having a substituent that is susceptible to the acid or base. In addition, these processes cannot allow, for example, a hydroxymethyl group, an alkoxymethyl group, an acyl group or a tertiary carbon atom to directly combine with a carbon atom constituting an unsaturated boned of an unsaturated compound or with a methine carbon atom of a bridged cyclic compound.
Addition reactions to a carbon-carbon double bond in accordance with a radical mechanism or coupling reactions to form a carbon-carbon bond are also known. However, there are few processes that can efficiently yield addition or substitution reaction products or derivatives thereof by action of, for example, molecular oxygen under mild conditions.
Japanese Unexamined Patent Application Publications No. 8-38909 and No. 9-327626 each propose an oxidation catalyst comprising an imide compound having a specific structure or the imide compound in combination with, for example, a transition metal compound as a catalyst for oxidizing an organic substrate with molecular oxygen. Japanese Unexamined Patent Application Publication No. 11-239730 discloses a process, in which a substrate is allowed to react with at least one reactant selected from (i) nitrogen oxides and (ii) mixtures of carbon monoxide and oxygen in the presence of the imide compound and thereby at least one functional group selected from nitro group and carboxyl group is introduced into the substrate. PCT International Publication No. WO00/35835 discloses a process, in which two compounds are allowed to react with each other in the presence of a specific imide compound and a radical generator with respect to the imide compound and thereby yield an addition or substitution reaction product or an oxidized product thereof in accordance with a radical mechanism. These processes using the imide compounds can introduce an oxygen-atom-containing group such as hydroxyl group, nitro group or carboxyl group into a substrate or can form a carbon-carbon bond. However, they are still insufficient in yields of the target compounds, stability of the catalysts or amounts of the catalysts.